The production of sodium cyclacillin has been fraught with problems due to the form of the product which is either non-isolable in conventional filtration equipment or so hygroscopic as to be very difficult to handle in processing subsequent to its recovery from the reaction medium. Heretofore, only the hydrated forms of sodium cyclacillin could be isolated satisfactorily in conventional filtration equipment. However, the hydrated forms of sodium cyclacillin are extremely hygroscopic, presenting a relatively non-uniform product which impares quantitative measuring techniques of sampling, weighing, dispensing, and the like, as well as presenting storage stability problems. Previous attempts to produce anhydrous sodium cyclacillin by employing anhydrous conditions throughout the processing procedure have afforded a material which was non-isolatable in conventional filtration equipment due to its particle size and/or form.